0030279: HTML5: It should be possible to remove Android/iOS browsers need to download all sounds on game start

Description

It should be possible to remove the change we made in 2.1.5 to respond to a Change in Chrome which had the result that Android/iOS browsers need to download all sounds on game start. Now that 2.2.1 has the full "permission system" Safari and Chrome want to use, the game should be able to go back to streaming sounds on-demand following a touch by the player.

This would then greatly reduce loading times and memory usage by games which have a lot of audio files.

Steps To Reproduce

1. Start a game which has a few audio files on HTML5 in 2.2.0 / early 2.2.1 betas.
2. Observe the loading bar takes a little while - especially compared to Windows, say.
Repro: 100%